How do I get sinon to resolve a stubbed promise?

So I have this code stubbing a promise:

const getClientStub = sinon.stub(authenticationUtils, 'getClient').resolves(auth0ClientMock);

This code is question is this:

export const getClient = async (): Promise<Auth0Client> => {
  return await createAuth0Client({
    domain: window.globalConfiguration.auth0Domain,
    client_id: window.globalConfiguration.auth0ClientId,
    useRefreshTokens: true,

    // this forces the user to re-authenticate when the user has logged out of the application
    prompt: 'login',

    // this need to match the audience that the server that we send jwt token to using for the token to be
    // considered valid
    audience: window.globalConfiguration.audience,
  });
};

I know the mock it being called however the result of the mock is not resolving and whwn I log out the result of the mock I get:

Promise { <pending> }

I have mocked promises in the past with sinon however it has been a while since I needed to do that.

What I am doing wrong? How do I get the mocked stub to resolve the promise?